The present invention relates to a supporting structure for a motor rotor, and more particularly to a technique applicable to the small fan motor.
Generally, a fan motor constructed such that a motor rotor having a rotating body including blades secured to a motor shaft is supported by a bearing of a housing body having a stator is made practicable.
This fan motor has a type in which a metal bearing including an oil-impregnated sintered bearing is used and a type in which a radial ball bearing is used.
In the case of the metal bearing, as shown in an essential cross-sectional view of FIG. 5, a motor rotor in which a mount base 110 of a rotating body including the blade is fixed to a motor shaft 106 by insert molding is supported by a metal bearing 105 of a housing body 1 provided with a stator. As shown in drawing, the mount base 110 has a cone-shaped portion 110a partially formed so as to prevent splashing of the lubricating oil moving along the motor shaft 106 due to a centrifugal force developed along with the rotation, so that the lubricating oil passing from a shaft supporting portion is returned to the metal bearing again.
Also, in the case where the radial ball bearing 120 and the metal bearing 105 are provided as the bearing, a shaped portion 110a as shown is provided to give a pre-load to the inner ring of the radial ball bearing 120, as shown in an essential cross-sectional view of FIG. 6.
However, in this related machine type, the motor rotor with an exclusive shaped portion for each machine type has to be prepared, and correspondingly a specific metal mold has to be prepared, leading to a problem that the manufacturing process is complicated and the costs are increased.
Accordingly, the present invention has been achieved in the light of the above-mentioned problem, and it is an object of the invention to provide a motor rotor supporting structure in which a motor rotor with a body of rotation secured to a motor shaft is supported through a bearing of a housing body having a stator, which is applicable in both types of a oil-impregnated sintered metal bearing and a radial ball bearing, thereby preventing the manufacturing process from being complicated, and the costs from increasing.
In order to solve the aforesaid object, the invention is characterized by having the following arrangement.
(1) A motor rotor supporting structure comprising:
a motor rotor which includes a motor shaft and a rotating member including a blade secured to the motor shaft;
a bearing, for supporting the motor rotor, provided to a housing body including a stator; and
an annular groove portion, for preventing splashing of lubricating oil integrally, formed with and extending from a mounting base of the motor shaft to which the motor shaft of the motor rotor is secured, wherein an inner portion of the annular groove portion is adapted to receive a spacer portion abutted to an inner ring of a radial ball bearing so that the motor rotor is applicable to both a metal bearing and a radial ball bearing.
(2) The motor rotor supporting structure according to (1), wherein the metal bearing includes an oil-impregnated sintered metal bearing.
(3) The motor rotor supporting structure according to (1), wherein the spacer is not attached to the inner portion of the annular groove portion when the metal bearing supports the motor rotor.
(4) The motor rotor supporting structure according to (1), wherein the spacer is attached to the inner portion of the annular groove portion when the radial ball bearing supports the motor rotor.